Session Item

Intraoperative radiotherapy (IORT) of cranial cavities is performed immediately after resection of brain metastases or glioblastoma. Surgical hemostatic patches are usually placed for bleeding control. We measured the depth dose curve (PDD) of the 50-kV intraoperative radiotherapy device INTRABEAM (Carl Zeiss Meditec AG, Oberkochen, Germany) on various surgical patch combinations.

A water phantom and a soft jet ionization chamber in a water tank were used for this purpose. An electrometer gathered information on 10-second charges. Five depth-dose curves were recorded at a 40-µA beam flow and 50 kV, using a 3.5 cm spherical applicator. The applicator-chamber distance was adjusted in 13 different 1-mm layers and posteriorly displaced in a 3-mm fashion, from a 0.18 mm to a 1.18 mm depth. Two patches from different manufacturers were used for assessing different thickness levels, TachoSil (Corza Medical, MA, US) and Tabotamp (Ethicon, J&J Surgical Techonologies, NJ, US). Five measurements were performed with combined layers: 1) PDD reference curve (applicator only), 2) PDD + 1 TachoSil, 3) PDD + 2 TachoSil, 4) PDD + 2 TachoSil + 1 Tabotamp, 5) PDD + 2 Tabotamp

No significant dose delivery differences were identified (< 1%) with a single layer of activated TachoSil (approximately 1 mm thick). When the used in two layers, a 25% reduction in absorption was found. The combination of TachoSil and single-layer Tabotamp (300µm) did not attenuate significantly the absorption rates (< 2%).

During brain IORT, employing surgical hemostatic patches should be carefully regarded. Intraoperative imaging could help ease a real-time assessment of applicator-tissue contact and online Monte Carlo planning.